Gamma-amino butyric acid (GABA) is an inhibitory neurotransmitter which is thought to be involved in several neurological and psychiatric diseases. Although most GABA occurs in the central nervous system, small amounts of GABA are found in blood, and levels of plasma GABA may reflect its activity in brain. In several preliminary studies (supported in part by a NIMH Mental Health Small Grant) we have found levels of plasma GABA to be very low in recently detoxified patients with alcoholism, compared to controls and to patients with several other psychiatric diseases. The low plasma GABA levels were not correlated with several indices of severity of illness, such as amount of alcohol consumed, age, or duration of heavy drinking. Therefore, plasma GABA may represent a trait marker for the illness of alcoholism. We will test this hypothesis. First, a larger group of non-alcoholic controls will be studied to determine the stability of plasma GABA over time. Second, a series of patients with the diagnosis of alcoholism will have their plasma GABA levels determined on admission to an inpatient treatment unit, 28 days later at time of discharge, and on six month followup. A group of these patients will also have cerebrospinal fluid GABA measured to determine its correlation with plasma GABA. The hypothesis to be tested would predict that plasma GABA levels will remain low, even in those subjects who maintain sobriety. This research should contribute to our understanding of the role GABA plays in the pathophysiology of alcoholism